Brutal Doom received public recognition by John Romero himself during the IGN gameplay video made for the 20th anniversary of Doom, stating that if they had released Brutal Doom instead of Doom back in 1993, they "would've destroyed the game industry" and that "Brutal Doom is hilarious" (said at 1:08:48).

Perhaps the most obvious and eye-catching feature of Brutal Doom is the adding of features like additional blood (blood gets splattered on walls and ceilings if enemies or the player get hit), the ability to blow off body parts with strong weapons like the shotgun, and the addition of special iluminating effects on projectiles and pick ups. It is compatible with the source ports ZDoom, GZDoom, Skulltag, and Zandronum.

While primarily a gore mod, it goes further and alters the gameplay by changing many other aspects, such as the sounds, graphics, and combat.
One such change is the increased difficulty, making enemy behavior more unpredictable and dangerous (many attacks do double the normal damage to the player) and altering their attacks. It makes the animations smoother and gives the player new abilities.

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3D bloodspots allow all textures to be covered with blood, including the floor and ceiling.

A more dynamic interface. For example, blood splashes on the screen if the player kills an enemy up close, and glass cracks or bullet holes may appear on the screen when the player gets injured.

When the player is critically injured (30% health or lower), the screen gets stained with tiny blood splatters, and a dripping sound is played intermittently as the marine's blood drips continuously on the ground (albeit this is just a visual effect which adds to gameplay realism and does not incur in further health loss).

New death animations for all enemies. Body parts can be torn apart by shooting at various locations on the enemy's body with powerful weapons, cut in half with the chainsaw, melted with the plasma gun, burnt into smoky scorch by fire or electricity-based attacks, and blown to dozens of gibs by explosives.

Corpses can be further mutilated upon death. Note that this feature has been removed as of v19 in the name of bugfixing, but SgtMarkIV has stated he plans to re-add it.

Many enemies have new attacks (more details below), and many enemy attacks do up to twice the normal damage.

All of the standard weapons have been revamped with new graphics and sound, and most have had their functionality changed, such as by making it necessary to reload or by adding secondary functions (see below).

The berserk pack's capabilities are greatly expanded. With it, the player can perform fatality-style finishers on monsters. Killing monsters in this way will replenish a bit of health, depending on the enemy. As of version 0.19, Fatalities are performed at a faster speed and can overheal the marine, but now it heals 5 HP instead of 10. Note that for balance reasons, the player becomes invulnerable while the fatality animation plays. Other abilities include grabbing and throwing Lost Souls and explosive barrels, and using mortally wounded monsters as meat shields (a mortally wounded monster will be twitching in agony, making constant pain noises, and bleeding). A meat shield will absorb a set amount of damage from projectiles, at the cost of the player being limited to using only the rifle while carrying the shield. While carrying the shield, it can also be thrown to deal significant damage.

Implementation of headshots for all monsters — except for the Cacodemon, Lost Soul and Pain Elemental. Headshots deal as much as double damage (depending on the weapon), and can gib the monster's head for one of many special death animations (see the screenshot at the right). Autoaim does not assist in getting headshots. In fact, the "Weapon.NOAUTOAIM" flag has been added to all weapons to completely remove autoaim's function.

Invisibility spheres are replaced with captured marines. Punching or kicking a captured marine will free him and he will follow and aid the player against the demons. Captured marines spawn with random weaponry, with the stronger guns appearing less frequently. An allied marine can punch enemies at close range and even perform fatalities on them (like the player, becoming invulnerable in the process) to replenish his own health. However, any nearby demons will attempt to kill any restrained marines as soon as they are in the player's sight. If the marine is killed in battle after being freed, his weapon will be dropped for the player. Note that friendly fire against the friendly marines is enabled, it is possible to kill them both before and after setting them free.

If the player kills certain monsters by gibbing (or shreds their corpses with the chainsaw), they can sometimes take their weapons. This includes the Revenant's twin rocket launchers and the Mancubus's flame cannon, both mapped to key 8 (key 9 for the Mancubus cannon in version 0.18 onwards).

Enhanced lighting and shadow effects for decorations and projectiles similar to those found in the Doomsday engine.

Enemy bullets now act as projectiles, albeit very fast ones, allowing the player to dodge them given sufficient time and distance. They are generally more accurate than their hitscan-based vanilla counterparts, especially at a distance.

A kick attack has been added to shove enemies away from the player, similar to the one in Duke Nukem 3D. It is bound to Q by default. Like the fists, this attack is powered up by berserk as well. If performed in the air, it becomes a flying kick with the marine's foot turned 45 degrees, dealing even more damage. A "weaker" version of the flying kick can be performed on the ground as part of a combo (see below).

The fists are faster and can make quick jabs. Unlike in the "non-Brutal" Doom, they are now a silent attack and will not alert enemies. The alt-fire throws a slower but more powerful right-handed straight punch. Punching a Zombieman, Shotgun Guy, Heavy Weapon Dude or Imp from behind before the enemy has noticed will snap their neck, killing it instantly without alerting other enemies (this is especially easy to do at the beginning of MAP01 and MAP02 of Doom II and does not require a berserk pack).

A basic martial arts-style combo system was implemented in v19, allowing the player to quickly chain punches and kicks together with proper timing in attack key press. The "root" combo is comprised in this 3-hit punch sequence: left-hand jab, right-hand straight punch, left-hand horizontal hook punch, every one with increased power. Note that punches do not necessarily have to hit anything in order to activate one another. The third punch is capable of: knocking demons across the room, knocking Imps and zombies heads off and hitting Barons of Hell and Hell Knights in the crotch, stunning them and making them scream in pain. Also worth note, the third punch, even without the berserk pack power, will never perform fatalities or neck snaps, and will always gib/smash enemies to pieces without leaving their legs standing and/or attached. If the kick attack key is quickly pressed with correct timing right after any punch, a weaker version of the flying kick will be performed while on the ground (with either foot, depending of the punch used prior). The in-combo kick is stronger than the "regular" kick but weaker than the flying kick.

The chainsaw gets covered in blood splatters when sawing an enemy. It previously used the Doom 3 chainsaw sound but as of v19 it uses a improved Doom/Doom II sound.

The useless pistol is replaced by an automatic rifle, matching the player's sprite, which unlike the original pistol remains useful even late in the game. The rifle has a decent fire rate (close to the original chaingun) and is the most accurate weapon in the mod. The alt-fire mode allows the player to aim down the sights to snipe at enemies. It has a magazine size of 30.

The shotgun now fires ten pellets per shot instead of seven, to balance it with the Super Shotgun. Like the assault rifle, the sights can be used to reduce spread. It holds 8 shells, which are reloaded individually (and can also be shot "emergencially" in-between the reloading process by holding down the fire key). Aesthetically, it is now more tactical in style, giving it a black synthetic pump and stock instead of wooden ones, and also has a vented heatshield on the barrel.

The super shotgun receives an additional damage boost at point-blank range. It now has the option of firing only one barrel at a time, thus shooting only 10 pellets. It also has the ability to kill a Hell Knight (and sometimes a Baron too) with both barrels fired at close range at head-level (doing this point-blank results in the body hitbox getting in the way of the shot).

The chaingun is now correctly referred to as a minigun (as well as resembling the more traditional design of said guns), and fires 50% faster but also requires a spin-up and cool-off before and after firing. The alt-fire mode makes the barrels continuously spin, further increasing the firing rate but also drastically decreasing the accuracy and alerting monsters (due to spin noise). Unlike most of the reworked guns, it does not need to be reloaded.

The rocket launcher has a much smaller splash damage area, but it causes 50% more damage on a direct hit. It holds 6 rockets per clip.

The plasma gun deals roughly double damage and can cause minor splash damage to enemies (and players, if the bolt hits a nearby wall), but fires at a slower rate. As of v19, the alternate fire mode fires a continuous flamethrower-style spread of blue flames, inflicting great deal of damage over time but depleting the plasma cell extremely quickly. It has a clip size of 50.

The BFG9000 uses the Doom 3 BFG sound effects and the primary energy ball deals double damage. Instead of the original BFG's hitscan tracer attack, it simply deals damage in a very large radius, like an even more powerful rocket launcher.

Most weapons push the player back a tiny bit upon firing, especially the Super Shotgun and the BFG9000.

The player is able to flip monsters off while shouting rude comments like "go fuck yourself" (voiced by Danny Glover originally and now by Tony Danza) by a bindable command known as "offend". This command will alert nearby monsters as if the player had just fired a weapon as well as offend them (hence the name) causing some enemies to attack more frequently. There are other bindable commands, such as "wave". Pressing the wave button during a fatality (see below) will allow the player to see his own wave animation in third-person, however you can take damage while waving.

There are several voice acted taunts and one-liners voiced by Chinese Tony Danza, that can be spoken with keys J and K by default. Many of these quotes are taken straight from the infamous Doom comic. Note that as of version 0.19, these have been cut due to overuse in multiplayer games and will be in an optional mutator.

Both the Grenade Launcher and the Rail gun from the Skulltag source port have been given new sprites and attributes. The Grenade Launcher is a standard issue M79; it has a much larger blast radius than the Rocket Launcher, but fires much slower as well as dealing less damage. The Rail gun fires at a slower rate than the vanilla Skulltag Rail gun but uses half as much ammunition, has a scope for zooming in, and reloads after 5 shots instead of 4.

As of version 0.19, Zombiemen and Shotgun Guys can enter into a last stand and pull out a pistol when they have one of their limbs cut off. They will then die after getting shot a few more times.

Wolfenstein SS officers changed radically into soldiers in accurate SS uniforms with a demonic appearance and fanatical military voices. They possess more complex behavior, frequently dashing diagonally left and right, making them hard to hit. Their powerful MP40 submachineguns, mapped to key 8 (key 0 in v18), can be picked up and used by the player. The MP40 has a higher rate of fire than the assault rifle and a 32-round magazine. This was removed as of v19 but will be added in a optional mutator

The Imp now has a jumping pounce attack like the new imp from Doom 3 that it will use at close range, and can sometimes shoot two fireballs in quick succession. Its projectiles are now much more detailed, with several sound and visual effects. The player will have bloody slashes marking his screen in the direction an Imp connected with a melee attack.

Melee-oriented monsters, such as Hell Knight and the Demon, will perform fatalities on the player and even other monsters if they kill them with a melee attack.

Demons are faster, both in movement and attack speed. Because they are melee-only monsters, they will always perform any available fatalities on a successful kill, which includes biting lesser monsters in half and eating their entire upper body. Fatality: the Demon rips and chews the marine's upper body multiple times, splashing blood everywhere. In v20, the Demon(s) will also devour the flesh off the dead marine multiple times in a horrible predatory hunger.

Spectres are completely invisible, save for their eyes, making them much harder to detect — however, they briefly flash into a translucent state upon attacking and taking damage. They become visible upon death, with a red gaseous substance marking the kill.

The Cacodemon will frequently shoot two consecutive projectiles and can shunt itself out of the way of incoming attacks. It also floats a bit faster than its classic Doom counterpart. Aesthetically, their melee attack now has actual sound effects, unlike the classic Doom Cacodemon's silent gaping maw. Fatality: the Cacodemon bites a player to death, a sideways animation will be shown depicting the monster eating the player's upper torso then dropping the player's mutilated lower half to the floor as the monster squares back up to the camera. As of v 0.19, can be killed with a single shot from the super shotgun at point blank range.

The Hell Knight now can sometimes shoot three consecutive projectiles, in a similar fashion to the Imp and Cacodemon. Fatality: the Knight grabs the marine, throws him roughly to the ground and crushes his head with a curbstomp. As of v 0.19, can be killed instantly with a headshot from the super shotgun.

The Baron of Hell has gained two new projectile attacks: first, it can launch three of its fireballs in a wide spread, which takes longer for the Baron to wind up. The second attack is after a former human gets into a infight with the baron and the baron wins with a melee, the baron will either rip the head off (zombieman) or in half (former seargent) then throw the corpse at the player, dealing nearly 300 damage.

Chaingunners, Hell Knights and Barons of Hell can be kicked (Hell Knights and Barons can be 3-hit combo'd too) in the crotch , stunning them for a few seconds (applies only from version 0.18 onwards).

Arachnotrons are much larger, around the size of a Baron of Hell, and also move faster. Their plasma shots now are the same firing sound and blue projectiles fired by the player's own plasma gun.

Lost Souls now have half of their original health and deal less damage, but fly around and attack much faster, which can potentially cause unlucky or slow players to miss attacks constantly — making them one of the more frustrating enemies in the game. Their flames have been removed from the sprite and are now generated by particle emitters. Upon death, Lost Souls explode in a fire puff and leave small bony chunks on the ground. Also, they no longer bleed when attacked. As of v 0.19, when killed they emit the same death screams from their Doom 3new versions.

Pain Elementals explode upon death (unless killed via fatality), causing heavy damage to nearby environmental objects, monsters and the player as well.

Revenants always fire two guided missiles at a time (matching their animation of both shoulder cannons lighting up when firing), and non-guided missiles are fired in volleys of four. Guided missiles are slower, have a much more limited fly pattern (they tend to travel downwards to the ground unless they can reach their target or hit any obstacle) and are now indicated by a reddish glowing color. Non-guided missiles are fired more rapidly, fly faster and straighter, and glow with a yellowish lens flare effect. As of v19, Revenants can be cut in half (either by the chainsaw or blasted in two parts by the super shotgun or any explosive means such as the rocket launcher), after which their upper half will remain alive, dragging itself across the ground and attacking (though only by firing single missiles and no longer by punching). Fatality: Revenants may also pick up zombies and Imps, bash them into the ground several times and throw them at the player, dealing very high damage - often killing the player with a direct hit.

Mancubus fireballs have a blast radius that deals slight fire damage. They leave damaging flames for several seconds after hitting a surface.

An Arch-Vile's attack takes longer time to charge, however they can resurrect enemies without having to stop and face the monster's corpse. Their apperance has also changed, as they now have a new "soft death" animation and sport large stereotypical ram-like demon horns.

The Cyberdemon has a new melee attack: a devastating stomp which against the player always means instant death (a homage to the Doom 3 version). In addition, it shoots its fire-engulfed rockets faster and for longer (four per volley instead of three), in a wider angle, giving it a limited ability to lead its shots against circle strafing players. As of version 0.18, using the "Offend" command in front of the Cyberdemon will enrage him, drastically increasing his aggression, firing speed, and the amount of rockets fired per attack the cyberdemon can be offended 3 times unlike other monsters and roars when further enraged. Visually, its death animation has been enhanced with a massive 3D explosion that, in version 0.16 and below, will deal damage. As an aesthetic correction, the rockets are now fired from the Cyberdemon's rocket launcher arm instead of the middle of his legs.

The Spider Mastermind's gatling gun now fires high caliber explosive rounds, essentially a mini-rocket launching chaingun. Its reaction speed is now much faster, nearly instantaneous, giving the player little time to get out of its way. However, its projectiles travel slower than normal bullets, so with enough open space they can semi-reliably be avoided, not taking spread into account. Perhaps the most dramatic change to this monster is that it has four times as much health as its vanilla counterpart (12000 vs 3000); however, the "brain" portion of the Spider takes about 2.5 times more damage than normal. this combined with the 50% increase in rocket direct hit allows a skilled player to kill it faster than in vanilla Doom.

In certain versions, Commander Keen's head is replaced with that of infamous pop star Justin Bieber.

Decorative props, such as trees, hanging corpses and lights, can be destroyed. Destroying hanging corpses will occasionally reward the player with health and armor bonuses or stimpacks that were hidden inside them.

Brain gibs scattered on the floor.

As of version 0.19, brain pieces now scatter in walls after a headshot.

All moving entities now wade through liquids instead of walking on top of them (their sprite appears partially submerged), causing splashing sounds to play. The various liquid textures are also greatly enhanced.

Enemies randomly drop demon strength runes upon death, which act similarly to berserk packs (the only real difference being that they replenish only 10% of health, unlike the 100% health boost provided by the berserk pack).

Brutal Doom also has avalible downloads certain "mutators", or mods, that tweak the gameplay further; such as by changing the rifle back to a reskinned pistol, and giving the former humans the ability to speak and taunt the player.

In versions prior to 0.19, corpses could be mutilated upon death. This feature was removed in 0.19 because it caused bugs. This also prevents you from obtaining the Revenant and Mancubus weapons as you can't use the chainsaw on their bodies anymore. Note that according to Brutal Doom's creator, this feature will be re-added as an optional mutator.

In versions prior to 0.19, there was ammunition change such as having the bullets use 300 ammo (and 600 with the backpack) and the BFG expanding to 50 cells per shot, these features were removed in 0.19 because they were breaking compatibility with wads using DEHACKED.

In versions prior to 0.18, firing hitscan-based weapons too close to walls and other solid surfaces dealt minor shrapnel damage to whatever was too close (namely players and zombies finding themselves on the wrong end of bullet spread in a narrow corridor).

In v18, the minigun's continuous fire produced a recoil which constantly pushed the player's aim upwards (this was removed in v19).

In v18, a dodge system was introduced, allowing some enemies (mostly the weaker ones, such as Zombies, Imps, Cacodemons and Lost Souls) to occasionally dash/roll/fly sideways to avoid projectile attacks. This was removed in v19 (except for Cacodemon and Lost Soul) but will be added in v20 as an optional mutator.

In versions prior to 0.19, the plasma gun's secondary fire was a shotgun-like burst of plasma that could up to twice as much damage as a rocket. It was replaced in v19 by a blue "flamethrower"-like attack, but for v20 the mod creator intends to re-implement the old "shotgun spread" for the plasma gun and transfer the "flamethrower" attack as a secondary fire for the Mancubus flame cannon.

In versions prior to 0.19, the BFG9000 energy ball could fatally injure the player if it exploded too close (only applied if it hit an inanimate object or obstacle instead of an enemy).

The Cyberdemon had the ability to launch grenades as well as rockets.

In early versions, the Spider Mastermind possessed a BFG.

In versions prior to 0.17, both the Cyberdemon's and Spider Mastermind's exploding death animations dealt heavy damage (or instant death) to anything near the explosion — in newer versions, they still explode violently upon defeat but dealing no damage at all. This was likely removed due to maps requiring the player to telefrag such bosses.

Chaingunner 2 - the Marine tackles the zombie chest-first onto the ground, then hops foot-first onto his back and rips out both the zombie's arms. The enemy bleeds and screams to death, allowing the Marine to crush/blast his head for an extra health boost.

Imp 1 — the player throws the Imp to the ground belly-first, and crushes its head with a stomp (spinning his foot to smear the brains afterward).

Imp 2 — the player grabs the Imp's spine and tears it out, completely mutilating the imp.

Demon 3 - the player knees the Demon in the head multiple times before throwing it to the ground and stomping its head in.

Lost soul - this is not exactly a fatality, but a weapon. The player grabs the Lost Soul and it can be thrown at an enemy by jabbing dealing enough damage to kill up to an Imp instantly, the flaming corpses deal damage for a shot time, you can still straight while holding him, and even put him away without killing him. Pressing the reload key crushes the lost soul

Cacodemon 1 — same as Demon 2, but the player uses his foot to press the Cacodemon's lower jaw downwards, facilitating the execution.

Cacodemon 2 — the player punches through and rips out the Cacodemon's single eyeball.

Pain Elemental 1 - the Marine rips out one of the Elemental's black horns and knocks over the Elemental, then climbs on and stabs the horn into its eye multiple times before shaking it (while the horn is still shoved into the monster).

Baron of Hell 1 — The Baron lunges at the marine, who dodges by rolling behind it. From behind, he rips the Baron's spinal cord out with its head still attached, like Mortal Kombat character Sub-Zero.

Arachnotron 1 — The player rips out one of its mechanic legs, causing the Arachnotron to fall and emit its death sound (while making an "Oh, shit!" facial expression), then the player drives the amputated mechanic leg into the creature's face, destroying it completely.

Arachnotron 2 - the marine rips the brain out of its mechanical chassis, causing it to crawl away while bleeding to death, it can be kicked to bounce around and eventually die or shot to just deal damage and kill it without bouncing it around, if it bleeds out it will have a peaceful look on its face with blood dripping out, if you kill it it will explode into a pile of brains. The corpse of the brain can be destroyed even after death.

Revenant 1 — the Marine tears off the Revenant's arm, causing him to kneel before him. The Revenant roars in contempt, right before the marine uses the arm to smash his skull off like a baseball, the head can damage and even kill other enemies.

Revenant 2 - the Marine pulls down the Revenant's spinal cord, causing the monster to fall to pieces.

Arch-Vile 1 — the player rips the Vile's body horizontally in half.

Arch-Vile 2 — continuing from Vile 1, the Marine then tosses the upper half to the right (the lower half collapses sidewards to the left by itself) and crushes it with a powerful stomp, then lets out a triumphant laugh.